Analytical instruments have found use in modern laboratories for performing a large number of routine analyses. Accordingly, such instruments require the handling and processing of a large number of samples during a day of typical use. Quite often, the samples assume a liquid form. Accordingly, they and their containers must receive careful handling in order to avoid the loss of the samples themselves and the possible contamination of their surrounding environs. The latter becomes a particularly egregious problem where the sample contains radioactive or infectious material.
An operator's manual insertion of a sample tube into an instrument immediately prior to its analysis and its removal immediately afterwards has proven very inefficient. Initially, it requires the constant and total attention of the operator. The expenditure for such an individual immediately imposes a heavy economic burden upon the running of each assay.
Furthermore, the operator simply cannot replace an assayed sample with an unknown sample in the instrument with much speed. Consequently, the efficiency of the instrument, which must sit idle while waiting for the next sample, suffers further.
Additionally, replacing sample tubes in the instrument represents a boring, unchallenging task. As a result, the operator may not devote his full attention to its proper performance. Consequently, the very nature of the effort required of the operator may lead to its incorrect performance with concommitant inaccurate and possibly seriously deleterious results.
Thus, many instruments have undertaken to automatically handle a multitude of sample holders in addition to their normal more usual performance of particular analyses upon the samples. Some of these sample-changing instruments attempt to handle a number of sample holders placed individually into a retaining device. The device then subsequently moves the individual samples to the instrument's detector. These instruments which accept only individual sample tubes have only limited capacity. They also continue to require substantial attention becuase of the necessity of handling each of the sample tubes going into the instrument. Lastly, they incorporate complicated mechanisms for receiving, holding, and moving the individual sample tubes.
U.S. Pat. Nos. 3,187,182 to J. Fratantuno; 3,270,202 to M. J. Long et al.; 3,348,658 to R. E. Cannon; and 3,355,454 to R. E. Olson et al. provide examples of such instruments requiring the individual insertion of tubes into a sample changer. In each of these patents, the tubes follow a convoluted, circuituous path across the surface of the tray to reach the detector. The twisted, contorted path provides a greater capacity to the instrument's surface.
This type of device further requires a type of chain device providing holders for the individual tubes. The motion of the chain provides the power to move the tubes. An operator catching his finger in the train could suffer serious personal injury. Alternatively, the tray may avoid the chain drive, but rather require a surface completely full of tubes. This latter alternative restricts the instrument's flexibility.
L. E. Packard et al., in their U.S. Pat. No. 2,924,718, and L. R. Heiss in his U.S. Pat. No. 3,322,958, show devices in which the sample tubes occupy positions in the periphery of a wheel. As the wheel moves, it either brings the tubes to a position where a carrier may move it to the detector, as in the former, or to the detector itself, as in the latter. However, permitting only a circle of the sample tubes severely limits the capacity of the instrument.
In an effort to achieve greater efficiency, other instruments have attempted to receive and operate upon trays each carrying a multitude of sample holders. However, the instrument becomes limited by the necessity of determining the position of the sample tubes within the trays themselves. Thus, they must first achieve relative motion between the detector in the instrument and the trays. They must also properly locate the sample tubes relative to the exterior configuration of the trays.
The sample trays in these instruments remain totally passive. They do not assist the instrument in the proper location of the tubes relative to the detector. As a result, the instruments must incorporate sufficient and sufficiently sophisticated components to bring the sample tubes and the detector together.
Furthermore, the trays for a particular instrument can possess very little degree of variability from each other. Any change in their configuration will very likely confuse the instrument and hinder, if not absolutely prevent, the proper handling of the sample tubes inside the tray.
As examples of instruments using such sample trays, the U.S. Pat. Nos. 3,062,764 to W. W. Allen et al.; 3,859,528 to S. H. Luitwieler, Jr., et al.; and 4,040,533 to W. J. De Boer all show sample trays having a one-dimensional array of tubes. The instrument attempts to move the trays along various paths on the top of a flat table in order to bring the sample tubes to the detector.
O. G. H. Junger et al., in U.S. Pat. No. 3,327,833, goes a step further and provides a mechanism moving such sample trays vertically as well as horizontaly. As with the prior patents, the trays all have the same configuration in order to permit the instrument to handle them properly.
L. E. Packard et al., in their U.S. Pat. No. 3,257,561, show instruments incorporating circular trays having sample tubes at their periphery. The patent then discloses an extremely complex mechanism for shifting each tray from one stack of unanalyzed samples to another stack after the testing procedure.
Further, U.S. Pat. Nos. 3,855,473 to J. E. Burgess et al. and 3,911,274 to C. J. Roos et al. show instruments utilizing trays with two-dimensional arrays of sample tubes. However, the trays remain motionless and require the detector, in both instruments, to have two degrees of freedom of motion in order to find the sample tubes. The trays in the former of the two patents have absolute regularity for this purpose. In the latter case, the operator may place strips of light sources on the instrument itself to help it find the tubes within the trays.
U. S. Hof et al.'s U.S. Pat. No. 3,654,472 places trays with two-dimensional arrays of tubes on carriers in a "Ferris wheel" arrangement. The instrument must not only move the trays around the circuit, but it must also move each tray out of its carrier past a detector. Again, the passive nature of the tray requires that they all be the same in order that the instrument may handle them properly.
In U.S. Pat. No. 3,722,719 to E. Frank appears an instrument which moves trays having a two-dimensional array of tubes linearly past a carriage station. At the station, the entire row of tubes enters the carriage which transports them together to the detector. Again, for predictability, the trays all resemble each other and must fit within a particular carrier which provides them with their mode of power.